JP4386063B2 - Method for producing light diffusing methacrylic resin multilayer board - Google Patents

Description

  The present invention relates to a methacrylic resin multilayer board having light diffusibility.

  As a methacrylic resin plate having light diffusibility, (1) a compound in which a light diffusing agent is blended to impart internal diffusibility, (2) a surface provided with irregularities to impart external diffusibility, (3) What provided these internal diffusibility and external diffusivity together is generally known. In addition, (4) a multilayer structure having a light diffusing layer and a transparent layer due to internal diffusibility, and (5) a multilayer structure having a light diffusing layer and a transparent layer due to internal diffusivity and external diffusivity are variously studied. ing. (For example, refer patent documents 1-4).

Japanese Patent Laid-Open No. 55-113561 JP-A-56-151560 JP-A-57-18251 JP-A-1-138211 JP-A-6-344359

  When a methacrylic resin plate having light diffusivity is applied to an internally-illuminated signboard or a light diffusing plate for a display board provided with a light source, the methacrylic resin plate may be a light as described in (4) or (5) above. A multi-layer structure having a diffusion layer and a transparent layer is preferably used because the light diffusion layer has a depth and a high-class feeling due to the transparent layer, but the light diffusivity is not always sufficient, so that the light source is transparent. There was a problem that it was easy to see and brightness unevenness was likely to occur. Further, when the blending amount of the light diffusing agent is increased in order to improve the light diffusibility, there is a problem that the light transmittance is lowered and the luminance is lowered.

Accordingly, an object of the present invention is to provide a method for producing a methacrylic resin plate having a multilayer structure in which a light diffusion layer is deepened by a transparent layer and has a high-class feeling, excellent light diffusibility, and excellent light transmittance. is there.

As a result of intensive studies, the present inventors have found that the above object can be achieved by producing a methacrylic resin plate composed of three layers each having a predetermined total light transmittance, haze and thickness by a predetermined polymerization method. The present invention has been completed.

That is, the present invention includes a first layer below a method for producing a Rume methacrylic resin multilayer board having a second and third layers, contain a light diffusing agent, a resin having a characteristic of the first layer Using a cell with a plate on one side, a syrup containing a monomer mainly composed of methyl methacrylate and a polymer composed mainly of methyl methacrylate and constituting the third layer by polymerization was poured into this cell. A method of producing a methacrylic resin multilayer board that is polymerized after forming an intermediate layer that can constitute a second layer by polymerization by diffusing a light diffusing agent from the resin board near the interface of the syrup layer. It is to provide.
First layer: a layer having a total light transmittance of 3 to 80%, a haze of 90% or more, and a thickness of 2 to 10 mm.
Second layer: present between the first layer and the third layer, the total light transmittance is 30 to 90%, and is higher than the total light transmittance of the first layer, and the haze is 80% or more, And the layer whose thickness is 1-3 mm lower than the haze of a 1st layer.
Third layer: a layer having a total light transmittance of 90% or more, a haze of 1% or less, and a thickness of 1 to 10 mm.

According to the present invention , a light-diffusing methacrylic resin multilayer board can be produced which has a high-quality feeling due to the depth of the light-diffusing layer due to the transparent layer, is excellent in light diffusibility, and is excellent in light transmittance .

  The light-diffusing methacrylic resin multilayer board of the present invention is composed of a first layer, a second layer, and a third layer having predetermined total light transmittance, haze and thickness, respectively. Here, the methacrylic resin which is a base resin constituting each layer may be a homopolymer of methyl methacrylate, or 50% by mass or more of methyl methacrylate and 50% by mass or less of other monomers. A copolymer may also be used.

  In the case of a copolymer, the monomer composition is preferably 65% by mass or more of methyl methacrylate, 35% by mass or less of other monomers, and more preferably 80% by mass or more of methyl methacrylate. The other monomers are 20% by mass or less.

  In the case of a copolymer, examples of monomers other than methyl methacrylate include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, acrylic Acrylic esters such as cyclohexyl acid, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, methacrylic acid such as cyclohexyl methacrylate, phenyl methacrylate Examples include methacrylic acid esters other than methyl acid, acrylic acid, methacrylic acid, maleic anhydride, styrene, cyclohexylmaleimide, acrylonitrile, etc., and two or more of these are used as necessary. And it can also be.

  In addition, the methacryl resin which comprises each layer may be mutually the same, and may differ.

  The first layer is a light diffusing substrate layer for the methacrylic resin multilayer plate of the present invention to function as a light diffusing plate.

  The total light transmittance of the first layer is 3 to 80%, preferably 10 to 70%. If the total light transmittance of the first layer is too low, the light transmittance of the multilayer board will be insufficient. On the other hand, if the total light transmittance of the first layer is too high, it becomes difficult to increase the haze of the first layer, so that the light diffusibility of the multilayer board becomes insufficient.

  The haze of the first layer is 90% or more, preferably 95% or more. When the haze of the first layer is lowered, the light diffusibility of the multilayer board becomes insufficient.

  The thickness of the first layer is 2 to 10 mm, preferably 3 to 8 mm. If the first layer is made too thin, the light diffusibility of the multilayer board becomes insufficient, and the surface state of the first layer tends to change when the multilayer board is manufactured or used. On the other hand, if the first layer is made too thick, the thickness of the multilayer board becomes unnecessarily thick, making it heavy and difficult to use.

  The total light transmittance and haze of the first layer can be adjusted by blending a light diffusing agent having a refractive index different from that of the methacrylic resin of the base material. Usually, as the blending amount of the light diffusing agent is increased, the total light transmittance is lowered and the haze is improved, so that the haze is 90% or more and the total light transmittance is not less than 3%. What is necessary is just to adjust the compounding quantity. Examples of the light diffusing agent include inorganic particles such as calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, and zinc oxide, and these inorganic particles. Organic particles such as those subjected to surface treatment with fatty acid, crosslinked or high molecular weight styrene resin particles, crosslinked or high molecular weight acrylic resin particles, and crosslinked siloxane resin particles may be mentioned. Two or more kinds can also be used. Further, by providing surface irregularities on at least one surface of the first layer, preferably the surface opposite to the second layer, external diffusibility can be imparted and haze can be adjusted. The first layer may contain additives such as organic pigments and inorganic pigments, organic dyes and inorganic dyes, antioxidants, ultraviolet absorbers, mold release agents and the like as necessary.

  The second layer is a layer that exists between the first layer and the third layer and has light transmittance and light diffusibility between the first layer and the third layer.

  The total light transmittance of the second layer is 30 to 90%, preferably 50 to 90%. If the total light transmittance of the second layer is too low, the light transmittance of the multilayer board becomes insufficient. On the other hand, if the total light transmittance of the second layer is too high, it becomes difficult to increase the haze of the second layer, so that the light diffusibility of the multilayer board becomes insufficient.

  The haze of the second layer is 80% or more, preferably 95% or more. When the haze of the second layer is lowered, the light diffusibility of the multilayer board becomes insufficient.

  The thickness of the second layer is 1 to 3 mm, preferably 1.5 to 2.5 mm. If the second layer is too thin, the light diffusibility of the second layer is difficult to be uniform, and the light diffusibility of the multilayer board becomes insufficient. On the other hand, if the second layer is too thick, the thickness of the multilayer board becomes unnecessarily thick, making it heavy and difficult to use.

  Furthermore, the total light transmittance of the second layer is made higher than the total light transmittance of the first layer, and the haze of the second layer is made lower than the haze of the first layer. Thereby, the light diffusibility of a multilayer board can be improved. In the second layer, it is preferable that the total light transmittance continuously increases and the haze continuously decreases from the first layer side to the third layer side.

  Like the first layer, the total light transmittance and haze of the second layer can be adjusted by adding a light diffusing agent having a refractive index different from that of the methacrylic resin of the base material. The same one layer can be used. The second layer may contain additives such as organic pigments and inorganic pigments, organic dyes and inorganic dyes, antioxidants, ultraviolet absorbers, mold release agents and the like as necessary, as in the first layer. Good.

  The third layer is a highly transparent layer, and is a layer for obtaining a sense of quality by giving depth to the light diffusion layer composed of the first layer and the second layer.

  The total light transmittance of the third layer is 90% or more, preferably 92% or more. When the total light transmittance of the third layer is lowered, the light diffusion layer is less likely to be deep.

  Further, the haze of the third layer is 1% or less, preferably 0.5% or less. When the haze of the third layer is increased, the light diffusion layer is less likely to be deep.

  The thickness of the third layer is 1 to 10 mm, preferably 2 to 8 mm. If the third layer is too thin, the light diffusion layer will not be deep. On the other hand, if the third layer is made too thick, the thickness of the multilayer board becomes unnecessarily thick, making it heavy and difficult to use. In addition, as with the first layer and the second layer, in addition to the light diffusing agent, an organic pigment and an inorganic pigment, an organic dye and an inorganic dye, an antioxidant, an ultraviolet absorber, a release agent are also used for the third layer. Additives such as agents may be included, but the third layer is a layer that is highly transparent and deepens the light diffusing layer to obtain a high-class feeling. Even if included, the amount is considerably limited.

  The methacrylic resin multilayer board of the present invention composed of the first layer, the second layer, and the third layer, each having a predetermined total light transmittance, haze, and thickness as described above, has a predetermined total light beam corresponding to each layer. Each resin plate having transmittance, haze, and thickness may be separately produced by a cast polymerization method, an extrusion molding method, etc., and these resin plates may be manufactured by hot pressing, or these resin plates are bonded with an adhesive. However, in terms of productivity, a cell containing a light diffusing agent and a resin plate having the characteristics of the first layer placed on one side is used, and this cell is mainly composed of methyl methacrylate. Injecting a syrup that contains a monomer and a polymer mainly composed of methyl methacrylate and can constitute a third layer by polymerization, and diffuses a light diffusing agent from the resin plate near the interface of the syrup layer To allow polymerization Ri After forming the intermediate layer capable of constituting the second layer, it is desirable to manufacture by polymerizing.

  The syrup may be prepared by mixing a monomer mainly composed of methyl methacrylate with a polymer mainly composed of methyl methacrylate, or may partially polymerize a monomer mainly composed of methyl methacrylate. Further, the partial polymer may be prepared by mixing a monomer mainly composed of methyl methacrylate and / or a polymer mainly composed of methyl methacrylate. Examples of monomers other than methyl methacrylate that can be contained in a monomer mainly composed of methyl methacrylate are methacrylic acid that can be contained as a monomer unit in a polymer mainly composed of methyl methacrylate. Examples of monomers other than methyl are the same as those given as examples of monomers other than methyl methacrylate when the methacrylic resin is a copolymer.

  The partial polymerization of a monomer mainly composed of methyl methacrylate is usually performed using a polymerization initiator. Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2 '-Azobis (2,4-dimethylvaleronitrile), 1,1'-azobis (4-methylcumol), 1,1'-azobis (4-isopropylcumol), 1,1'-azobis (1- Azo initiators such as acetoxy-1-phenylethane), lauroyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxyiso Butyrate, tert-butyl peroxypivalate, tert-butyl peroxybenzoate, tert-butyl peroxyacetate Over peroxide initiators such as bets and the like. The amount of the polymerization initiator used is usually about 5 to 100 ppm by mass with respect to the monomer mainly composed of methyl methacrylate. The temperature of partial polymerization is appropriately adjusted depending on the type and amount of the monomer and polymerization initiator, and is usually about 60 to 90 ° C.

  The ratio of the monomer mainly composed of methyl methacrylate and the polymer composed mainly of methyl methacrylate in the syrup is appropriately adjusted in consideration of workability when injected into the cell. Based on the total, the former is 80 to 99.5% by mass, and the latter is about 0.5 to 20% by mass. The higher the latter content and the higher the degree of polymerization, the higher the viscosity of the syrup.

  The syrup usually contains a polymerization initiator, and may contain a polymerization regulator such as an alkyl mercaptan, a terpenoid compound, or an organic disulfide. Moreover, what was previously mentioned as an additive which may be contained in a 3rd layer may be included.

  Examples of the polymerization initiator are the same as those exemplified above as examples of the polymerization initiator that can be used in the partial polymerization, and the content thereof is mainly composed of a monomer mainly composed of methyl methacrylate and methyl methacrylate. The amount is usually 100 to 5000 ppm by mass, preferably 500 to 2000 ppm by mass, based on the total polymer.

  Examples of the alkyl mercaptan include 1-lauryl mercaptan, 1-octyl mercaptan, 1-dodecyl mercaptan and the like, and these are used alone or in combination of two or more. The content of the alkyl mercaptan is usually 500 to 3500 mass ppm, preferably 500 to 1000 mass ppm, based on the total of the monomer mainly composed of methyl methacrylate and the polymer mainly composed of methyl methacrylate.

  Examples of the terpenoid compound include cyclohexane-1-methyl-4-ethylidene, 1,4-cyclohexadiene, 1-methyl-1,4-cyclohexadiene, myrcene, limonene, α-pinene, β-pinene, α-terpinene. , Β-terpinene, γ-terpinene, and the like, and these are used alone or in combination of two or more. The content of the terpenoid compound is usually 50 to 150 ppm by mass, preferably 75 to 125 ppm by mass, based on the total of the monomer mainly composed of methyl methacrylate and the polymer mainly composed of methyl methacrylate.

  Examples of the organic disulfide include dimethyl disulfide, diethyl disulfide, di-n-propyl disulfide, di-n-butyl disulfide, diisopropyl disulfide, diisobutyl disulfide, di-sec-butyl disulfide, di-tert-butyl disulfide, dicyclopropyl. Examples thereof include disulfide, dicyclobutyl disulfide, dicyclopentyl disulfide, dicyclohexyl disulfide and the like, and these are used alone or in combination of two or more. The amount of the organic disulfide used is usually 10 to 5000 ppm by mass, preferably 10 to 1000 ppm by mass, based on the total of the monomer mainly composed of methyl methacrylate and the polymer mainly composed of methyl methacrylate.

  The syrup is polymerized by injecting the resin plate having the characteristics of the first layer into a cell provided on one side, and the cell is formed by interposing the resin plate and a substrate such as a glass plate or a stainless steel plate through a spacer. What is necessary is just to comprise by arrange | positioning at intervals. At that time, if a substrate such as a glass plate or a stainless steel plate is installed outside the resin plate, the surface smoothness on the outside of the resin plate and the surface unevenness when external diffusion is imparted are affected by the heat medium. Further, it is preferable that the surface of the substrate that contacts the resin plate is a matte surface because the surface smoothness and surface irregularity of the resin plate are more difficult to change.

  The polymerization of the syrup is usually performed by heating in a polymerization tank using water or air as a heat medium. The heating temperature should just be more than the decomposition temperature of the polymerization initiator contained in the said syrup, and is about 40-130 degreeC normally. From the viewpoint of reducing productivity and the amount of unreacted monomer, the heating temperature is preferably at least two stages so that the initial polymerization temperature is 40 to 80 ° C and the final polymerization temperature is 100 to 130 ° C. The polymerization time is appropriately adjusted depending on the composition of the syrup and the thickness of the target multilayer board, but is usually about 2 to 100 hours.

  The syrup is usually injected into the cell at a temperature of 35 ° C. or lower, preferably 30 ° C. or lower. The rate of temperature increase from this injection temperature to the initial polymerization temperature is slowed to 60 ° C./h or lower. Is preferred. If this rate of temperature rise is too fast, it is difficult to form an intermediate layer that can form the second layer by polymerization with a desired thickness and concentration of light diffusing agent, particularly when the cell size is 600 mm square or larger. Become.

  The thus obtained methacrylic resin multilayer board of the present invention has a light-diffusion layer with a transparent layer, has a high-class feeling, is excellent in light diffusibility, and has excellent light transmittance. It is suitably used for display signage members, building members, etc., as well as mold signs and light diffusion plates for display plates. Among them, in recent years, it is suitably used for internally illuminated signboards and display plate light diffusing plates that use LEDs with a significantly improved brightness and high light directivity as light sources.

  Examples of the present invention will be described below, but the present invention is not limited thereto. In addition, the measurement method thru | or evaluation method of the physical property in each example are as follows.

[Total light transmittance (Tt) and haze]
The measurement was performed according to JIS K7111.

(Light diffusivity)
Measured according to DIN 5036.

〔depth〕
A 50 mm square sample was visually observed from a direction of 30 ° with respect to the normal direction to evaluate whether or not there was a depth (O: with depth, x: without depth).

[In-plane uniformity]
A 50 mm square sample was visually observed from the normal direction to evaluate whether or not the transmitted light was uniform in the plane (O: uniform, x: non-uniform).

As the light-diffusing methacrylic resin plate, the following (1) to (4) having both mirror surfaces were used.
(1): “SUMIPEX 030” (thickness 5 mm) manufactured by Sumitomo Chemical Co., Ltd.
(2): “SUMIPEX 032” (thickness 5 mm) manufactured by Sumitomo Chemical Co., Ltd.
(3): “SUMIPEX 040” (thickness 5 mm) manufactured by Sumitomo Chemical Co., Ltd.
(4): “SUMIPEX 055” (thickness 5 mm) manufactured by Sumitomo Chemical Co., Ltd.

  Moreover, about each of said light diffusable tacryl resin plates (1)-(4), what provided the unevenness | corrugation on one side was used as light diffusable resin plate (1 ')-(4').

For these light-diffusing methacrylic resin plates (1) to (4) and (1 ′) to (4 ′), the total light transmittance, haze and light diffusivity are measured with the mirror surface as the exit surface, and from the mirror surface side. The depth and in-plane uniformity were evaluated, and the results are shown in Table 1.

Examples 1-8
To 100 parts by mass of methyl methacrylate, 0.002 parts by mass (2,20 ppm by mass) of 2,2′-azobisisobutylnitrile is added and polymerized at 70 ° C. to contain 5 parts by mass of a polymer having a viscosity average molecular weight of 1,500,000. A partially polymerized product was obtained. 15 parts by mass of this partially polymerized product was mixed with 85 parts by mass of methyl methacrylate, 0.08 parts by mass of 2,2′-azobisisobutylnitrile (800 ppm by mass), cyclohexane-1-methyl-4-ethylidene 01 parts by mass (100 ppm by mass), ultraviolet absorber [Sumitomo Chemical "Sumisorb 200"] 0.01 parts by mass (100 ppm by mass) and mold release agent [Toho Chemical Co., Ltd. Nord RS-710 "] 0.01 parts by mass (100 ppm by mass) was added, mixed, and degassed to obtain a methyl methacrylate syrup.

  A light-diffusing methacrylic resin plate shown in Table 1 was placed on a glass having a matte surface with a thickness of 10 mm and a 600 mm square, with the mirror side facing upward (the side opposite to the glass). A cell having a thickness of 10 mm and a 600 mm square mirror glass is placed on the light diffusing methacrylic resin plate via a vinyl chloride gasket having a thickness of 5 mm, and a cell having a space of 5 mm thickness between the light diffusing methacrylic resin plate and the mirror glass. Was made. The methyl methacrylate syrup was poured into this space and placed in an air oven. The temperature of the syrup at that time was 25 ° C. Next, the temperature of the air oven was raised to 62 ° C. over 60 minutes and held for 310 minutes, and then the temperature was raised to 120 ° C. while checking the reaction rate and held for 120 minutes. After the temperature was lowered, the frame was opened and the methacrylic resin multilayer board was peeled from the glass plate.

  Table 2 shows the total light transmittance and haze of the used light-diffusing methacrylic resin plate as the total light transmittance and haze of the first layer. The thickness of each layer of the resulting three-layer methacrylic resin multilayer board was measured with a magnifier, and the results are shown in Table 2. Further, the obtained methacrylic resin multilayer board is polished with a milling machine and an abrasive, and only the second layer is removed except for the first layer and the third layer, and the third layer is removed except for the first layer and the second layer. Only the haze and the light diffusivity were measured, and the results are shown in Table 2. Further, for the obtained methacrylic resin multilayer board, the total light transmittance, haze and light diffusivity were measured with the third layer side as the exit surface, and the depth and in-plane uniformity were evaluated from the third layer side, and the result Are shown in Table 2.

Comparative Examples 1-8
The light diffusing methacrylic resin plate shown in Table 1 and a transparent methacrylic resin plate [Sumipex 000] (thickness 5 mm) manufactured by Sumitomo Chemical Co., Ltd., both surfaces of which are mirror surfaces are mirror surfaces of the light diffusing methacrylic resin plate. Was attached to the inside (transparent methacrylic resin plate side) with chloroform.

  The thickness, total light transmittance and haze of the light diffusing methacrylic resin plate used are shown in Table 3 as the thickness of the diffusion layer, total light transmittance and haze, and the thickness and total light transmittance of the transparent methacrylic resin plate used. And haze are shown in Table 3 as the thickness of the transparent layer, total light transmittance and haze. In addition, for the obtained methacrylic resin multilayer board having a two-layer structure, the total light transmittance, haze and light diffusivity were measured with the transparent layer side as the emission surface, and the depth and in-plane uniformity were evaluated from the transparent layer side. The results are shown in Table 3. The methacrylic resin multilayer boards of Comparative Examples 1 to 8 each had a lower light diffusivity than Examples 1 to 8 using the same light diffusing resin board.

Claims (3)

First layer below a second layer and a manufacturing method of the third layer having a Rume methacrylic resin multilayer board, containing a light diffusing agent, was placed a resin plate having the characteristics of the first layer on one side A cell was used, and a syrup containing a monomer mainly composed of methyl methacrylate and a polymer mainly composed of methyl methacrylate, and constituting a third layer by polymerization was poured into the cell. A method for producing a methacrylic resin multilayer board in which an intermediate layer capable of constituting a second layer is formed by polymerization by diffusing a light diffusing agent from the resin board in the vicinity of the interface of the layers, and then polymerized.
First layer: a layer having a total light transmittance of 3 to 80%, a haze of 90% or more, and a thickness of 2 to 10 mm.
Second layer: present between the first layer and the third layer, the total light transmittance is 30 to 90%, and is higher than the total light transmittance of the first layer, and the haze is 80% or more, And the layer which is lower than the haze of a 1st layer and whose thickness is 1-3 mm.
Third layer: a layer having a total light transmittance of 90% or more, a haze of 1% or less, and a thickness of 1 to 10 mm. The method according to claim 1, wherein the syrup is injected at a temperature of 35 ° C. or lower, then heated to 40 to 130 ° C. at a rate of 60 ° C./h or lower, and then polymerized at the temperature. After injecting the syrup at a temperature of 35 ° C. or less, the temperature was raised to 40 to 80 ° C. at a rate of 60 ° C./h or less, then, after initial polymerization at the temperature, the temperature was raised to 100 to 130 ° C., The production method according to claim 1, wherein the final polymerization is then performed at the temperature.